The most common types of machines used for bending of bar stock, tubes, pipes, and extrusions are ram-type bending machines, three-roll benders, rotary compression benders, and rotary draw machines. While all of these machines can be utilized successfully to effect bending of certain types of workpieces, they all have limitations which make them less than ideal for certain situations. For example, rotary machines of both types can only bend workpieces into circular arcs and leave stop and start marks on the workpieces as a result of metal flow, while machines that effect stretch forming leave jaw marks at the ends of the workpieces which in some circumstances mean that at least portions of the workpiece are wasted.
According to the present invention a bending apparatus is provided which has unprecedented versatility and functionality, combining the best attributes of most of the prior art bending machines without the drawbacks associated therewith. The apparatus, and method of bending utilizing the apparatus, according to the present invention allow workpieces to be formed to virtually any shape that commercial prior art bending apparatus are capable of forming, provide independent control of components thereof to allow smooth bending of non-symmetric parts, optionally allow multi-point bending (e.g. three ninety degree bends), when effecting symmetric bends distribute excess metal to both ends for smoother and more symmetric bending without "stop and start" marks, effect bending by abutment engagement of the workpiece so that there are no jaw marks, as a result of having no obstructions on the top of the apparatus allowing bending of workpieces of any (unlimited) length, provide variable traction pressure to allow cold forging of workpieces for springback control, and by utilizing direct acting clamping of a workpiece provide constant pressure control of the clamp (with resultant workpiece thickness and wrinkling control).
According to one aspect of the present invention a traction bending apparatus for acting upon workpieces comprises the following elements: A stationary die support for mounting a die adjacent a first end thereof and having a second end remote from the first end, and an intermediate section between the first and second ends. At least a first control arm pivotally mounted at a first pivot axis to the die support at a first portion thereof, adjacent the die support second end. At least a first linear actuator pivotally connected to the first control arm at a second pivot axis and pivotally connected to the die support adjacent the die support second end at a third pivot axis, the first linear actuator providing powered pivoting of the control arm about the first pivot axis. At least a first traction arm pivotally mounted at a fourth pivot axis to the first control arm at a second portion of the first control arm, remote from the first portion of the first control arm, the fourth pivot axis adjacent but spaced from the second pivot axis. A workpiece engaging member associated with the first traction arm remote from the fourth pivot axis. And at least a second linear actuator pivotally connected to the first traction arm at a fifth pivot axis adjacent but spaced from the fourth pivot axis, and pivotally connected to the intermediate section of the die support at a sixth pivot axis, the second linear actuator providing powered pivoting of the first traction arm about the fourth pivot axis.
The apparatus preferably further comprises a stripper linear actuator mounted to the intermediate section of the die support for effecting movement of a workpiece bent at a die mounted by the die support first end away from the die support, and the clamping linear actuator for clamping the workpiece at a die mounted at the die support to provide workpiece thickness and wrinkling control. All the linear actuators preferably comprise hydraulic piston and cylinder assemblies, and a control mechanism is provided for controlling the linear actuators by selectively controlling supplied hydraulic fluid to the piston and cylinder assemblies. The control mechanism may comprise: a computer; a plurality of limit and pressure sensors providing input to the computer; a plurality of solenoids controlled by the computer for completely independently controlling the flow of hydraulic fluid to each of the hydraulic piston and cylinder assemblies; and an hydraulic pump controlled by the computer.
The workpiece engaging member preferably comprises a separate and distinct element extending outwardly from the traction arm and including a pin defining an axis and connected to the traction arm, and a roller surrounding the pin. The roller makes abutment (only) contact with the workpiece to effect bending.
According to another aspect of the present invention traction bending apparatus for bending workpieces is provided comprising the following elements: A stationary die support for mounting a die adjacent a first end thereof and having a second end remote from the first end, and an intermediate section between the first and second ends. First and second control arms pivotally mounted at first and second pivot axes, respectively, to the die support at a first portion of each, adjacent the die support second end. First and second linear actuators connected to the first and second control arms, respectively, providing powered pivoting of the control arms about the first and second pivot axes, respectively. First and second traction arms pivotally mounted at third and fourth pivot axes, respectively, to the first and second control arms at a second portion of the control arms, remote from the first portion of each control arm. First and second workpiece engaging members associated with the first and second traction arms remote from the third and fourth pivot axes. Third and fourth linear actuators connected to the first and second traction arms, respectively, providing powered pivoting of the traction arms about the third and fourth pivot axes, respectively. And a control mechanism for allowing at least one of manual, semi-automatic, and automatic control of the linear actuators to move the workpiece engaging members into operative association with a workpiece engaging a die mounted on the die support to effect desired bending of the workpiece.
The first and second linear actuators may be hydraulic piston and cylinder assemblies with piggyback pneumatic piston and cylinder assemblies to actuate associated limit switches (e.g. Reed switches). A stripper linear actuator and a clamping linear actuator are also preferably provided, and all of the linear actuators are preferably hydraulic piston and cylinder assemblies. The first and second linear actuators are pivotally mounted to the first and second control arms, respectively, at fifth and sixth pivot axes adjacent, but spaced from, the third and fourth pivot axes, while the third and fourth linear actuators are pivotally mounted at a first end of each to the intermediate portion of the die support at seventh and eighth pivot axes, respectively, and at a second end to each traction arm at ninth and tenth pivot axes, respectively, the ninth and tenth pivot axes being adjacent but spaced from the third and fourth pivot axes.
The control mechanism, which includes a computer, limit and pressure sensors, solenoids, hydraulic pump, and the like, comprises means for, after a workpiece is brought into operative contact with a die supported by the die support: Actuating the clamping linear actuator to clamp the workpiece to prevent wrinkling; then controlling the third and fourth linear actuators to swing the traction arms to move the workpiece engaging members into operative association with the workpiece, and apply pressure thereto; then controlling the first and second linear actuators to retract the control arms while the traction arms continue to apply pressure to the workpiece so that the workpiece conforms to the die mounted by the die support; then de-actuating the clamping linear actuator to unclamp the workpiece, and controlling the third and fourth linear actuators to swing the traction arms away from the workpiece; and then actuating the stripper linear actuator to push the bent workpiece away from the die supported by the die support.
According to yet another aspect of the present invention a method of effecting bending of a workpiece (typically a pipe or like tubular element, or an aluminum extrusion) using a stationary die, clamping flanges at the stationary die, and powered workpiece engaging elements, is provided. The method comprises the steps of substantially sequentially: (a) Bringing a workpiece into contact with the stationary die. (b) Effecting direct linear movement of the clamping flanges to provide constant pressure clamping of the workpiece at the die to control thickness and wrinkling of the workpiece. (c) Swinging the workpiece engaging elements into operative abutting contact with the workpiece, and applying pressure to the workpiece with the workpiece engaging elements. (d) While continuing to maintain pressure on the workpiece with the workpiece engaging elements, moving at least one of the workpiece engaging elements with respect to the stationary die to effect smooth bending of the workpiece while continuing operative abutting contact with the workpiece. And (e) after desired bending of the workpiece, swinging the workpiece engaging elements out of abutting contact with the workpiece, and releasing clamping of the workpiece.
The method also typically comprises the further step between steps (a) and (c), of bringing one or more follow blocks into engagement with the workpiece at a portion of the workpiece opposite the die; and wherein steps (c) and (d) are practiced with the workpiece engaging elements directly abutting the follow blocks and through the follow blocks engaging the workpiece. Also, there is typically the further step, after step (e) of effecting powered linear movement of the workpiece away from the die.
Steps (a) through (e) are typically practiced so that bending takes place in a generally horizontal plane without top constraints, so that any length workpiece can be bent. Steps (c) and (d) are typically practiced by applying a variable pressure with the workpiece engaging elements to effect cold forging of the workpiece for springback control. Also, steps (c) and (d) are: practiced by providing independent variable control of each of the workpiece engaging elements to provide smooth bending of non-symmetric workpieces.
Step (d) may be practiced by moving both of the workpiece engaging elements with respect to the die to effect smooth symmetric bending of the workpiece, with rolling operative abutment of the workpiece. Also the die may be provided with a shape that is either a circular arc, or clearly distinct from the circular arc in which case steps (a) through (e) are practiced so that the workpiece is bent with at least one bend clearly distinct from a circular arc.
It is a primary object of the present invention to provide a versatile and highly effective bending apparatus, and method of effecting bending of workpieces. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.